Sand martin

                                                                                      Riparia riparia

                                                                        Gobhlan-gainbhich

                                                             Sand backie

It’s been a while since I’ve been out, between work and the weather. Today the sun has emerged. A warm breeze blows down the glen. I need to walk – slowly, purposefully, hopefully.

          Normally I’m inclined to head upstream seeking out the energy of Achness Falls, but on learning last night that the birds I watched skim past the garden are sand martins, I thought I’d follow them. On a previous walk I had noticed the river cliffs towards the confluence were punctuated by nesting holes, but I was unsure which feathered or furred river dweller had dug them. Now I imagine it may be sand martins. Besides, I didn’t reach the meeting place of the Cassley and Oykel last time, and I want to see where the Kyle of Sutherland is fully formed. Downstream is the plan.

          I traipse over the humped bridge and carefully descend stone steps set in to the eastern rampart. These are wide and easy slabs compared to those on the west – straightforward enough to ascend, but I haven’t risked going down, not with my dodgy knee.

          This is the Rosehall Estate stretch of the River Cassley. Mown grass and huge carefully situated beech trees, planted avenue style. There are two river monitoring stations. Looking at the big water gauge, the first calibration is well above the actual water level. Not even the warm west wind could blow a riffle to reach up to it. I’ve been watching river levels here since I took up temporary residence in Rosehall nearly six months ago.  Only once did I notice it in spate – after the snow in February and March. Since then, it has sat low and slow in its course. I worry for the natal Atlantic salmon; they need plenty water in the channel to be able to clear obstacles such as the Achness Falls and reach their upstream spawning grounds. They also need the water cold. If water temperatures regularly exceed twenty-three degrees Celsius, Atlantic salmon will struggle to survive. I dip my hand in the water and there’s no bite to it. It’s late May and I would expect snowmelt from Ben More Assynt to keep flow rates high and temperatures cool, but the snow has already gone.

          Wondering if my concerns about river levels and temperatures were warranted, I had sent an email to Keith Williams, director of the Kyle of Sutherland Fisheries Trust. Keith confirmed efforts are underway to tackle these issues in the catchment saying we need more tree cover next to the river. Plans are in place, but it is, as he put it, a ‘battle against time.’

Wider land management issues are also at play:

          ‘Overgrazing by deer is a major issue within our catchment,’ wrote Keith, ‘a run up the Cassley highlights the lack of tree cover next to the river, and the abundance of deer.’

More trees will help shade the river to keep temperatures cool. They will also increase plant and animal biomass to support a vibrant, diverse and healthy riverine habitat. In the meantime, river temperatures are creeping up to dangerous levels with increasing frequency.  More immediate solutions are necessary to provide respite for the cold-water Atlantic salmon – they are an indicator of the health of our river catchments and watery ecosystems.

The Cassley has a series of artificial groynes. These arms of stone stretch at a forty-five-degree angle into the river channel to create salmon pools and prevent erosion during spate and flood. I walk between two of them on the dried-out river bed. A pool has been cut off from the flow and is opaque with algae. Plants have found root space among the cobbles and are in bloom. Common dog violet, plentiful on the grassy river meadow, glowing blue-bright against the silt-dusted gneiss pebbles.

          A soundtrack of birdsong leads me farther downstream. I keep stopping, peering into the few deep amber pools. There is scant evidence of Atlantic salmon, not even an anticipative heron perched on a boulder gazing into the sub-surface void. I worry some more – will they make it upstream in sufficient numbers this year to keep the population viable? I reach the divide in the track. Keep right along the river or straight on to the confluence? I keep on.

          Rosehall House is to my left. It’s a muckle piece of decaying architecture. Roof giving way and windows boarded up. Skeletal arms of climbing plants taking hold – claiming territory, softening the façade.  The Big House. It is emblematic of much that is wrong with these glens – managed for deer, grouse, sheep – for the rich. Maybe my prejudice is borne of genetic memory.

          I don’t linger. A fenced-off woodland offers shelter from the prevailing wind. Larch, birch, beech – bird cherry in full nose-filling blossom, the long limbs of Scots pine. An understorey of vivid clear-scented bluebell, blush-white cuckoo flower and blaeberry, still in bud.

          Then I hear them. I feel them disrupting and gliding the thermals. Then a flick past my line of sight. The surface of the river, slowly and intensely carving around a steep-sided meander – alive with them. The stratified sandy soil is drilled with near a hundred nest holes, the majority to accommodate diminutive sand martins interspersed with the burrowings of kingfisher and otter.

          Riparia riparia. I love the the repetition of the species name for sand martins. A meditation of the river bank. In Scottish Gaelic – once the language of Sutherland – sand martins are gobhlan-gainbhich – gobhlan indicating forked, like their tail; gainbhich is sand. They are sand backies in Angus Scots – backies being an old word for bats. A blue-haze early-summer sky stretches north and west towards the mountains of Assynt. Standing on tufted hummocks of grasses, bleached blonde by the elements, my foothold is wobbly as eyes divert upwards, sideways, upwards, backwards tracking the incessant wing beating and soaring of the sand martin colony close to the confluence. I am reminded of bats in my garden – the way they flit and swoop and swell and dart through the dusk sky. Like sand martins, feeding on the wing. Fixated, I watch one parent, then the other, darting in and several seconds later re-emerging; pausing momentarily on the edge of the tunnel entrance before soaring across the river channel and upwards to gather more mayflies for the young.

Sand martins are on the Green List of birds; a general population decline across Europe but increasing in Scotland. They are vulnerable though to the effects of drought affecting their overwintering grounds in the Sahel – the incidence predicted to increase because of climate change. An article in Nature found consistency in claims that the southern boundary of the Sahara desert has extended one hundred kilometres into the Sahel between 1950 and 2015. The effect of this desertification is habitat loss in sand martin’s wintering grounds of Sahelian West Africa, as well as increasing the flight hazard from sand storms as the birds migrate.

          What we witness on our natal rivers is not in isolation, it is part of a global consideration. Here in Glen Cassley, native tree planting will eventually provide not only shade, but root structures to mitigate against flood erosion. Fallen wood will create deep pools for Atlantic salmon and food sources for invertebrates benefitting both fish and bird. Deer management and eventually, reintroductions of beaver and apex predators could aid in the recreation of riparian habitats that support natural balance. But we also need to consider wider climate change mitigation strategies on a global scale if we are to have meaningful impact.

My neck cricks as I track their movements skyward. When the air pressure is high, as it is today, the insect zone ascends on the warm air and the sand martins follow. They are an avian barometer.

          The cirrus-specked sky is mirrored in a pool where the south east flowing River Cassley meets the north east bound Oykel to form the Kyle of Sutherland. Despite local and global challenges, the confluence is teeming with myriad energies cumulating in an orchestration of life at its most vital and life-enhancing. Riparia riparia, sand backies, seemingly oblivious to my existence. I’m glad of that.  I walk upstream once more, slowly, purposefully – hopefully.

With thanks to Dr Keith Williams of the Kyle of Sutherland Fisheries Trust.

Link to Nature article cited: https://www.nature.com/articles/s41598-020-61085-0

Header Image Credit: Elaine Morrison